Conventionally, an LED (light-emitting diode) device mounted on the housing of an image scanner is used to indicate the scanning stage of the image scanner. For example, the LED device emit no light to mean that the image scanner is in an off-line state, and on the contrary, the LED device emits light to indicate that the image scanner is in an on-line. If the light emitted by the LED device is continuous, it indicates that the image scanner is in a standby state, and if the LED device emits twinkling light, it indicates that the image scanner is in an image-reading state. In addition, the LED device may emit light of another color to warn that the image-scanning operation cannot be performed or go on.